Electromagnetically energized oscillating head for spark erosion machine

ABSTRACT

924,617. Reciprocating motors. NASSOVIA WERKZEUGMASCHINENFABRIK G.m.b.H. July 24, 1961 [July 23, 1960], No. 26793/61. Class 35. [Also in Group XXII] Means for oscillating the electrode of a spark erosion machine in its direction of feed comprises an electrode support 5 mounted within a housing 1 on at least two spring elements 11, 12 having an adjustable pre-stress in the direction of oscillation which is produced by an electromagnet 2 through an air gap 8. The support 5 is screwed to an armature 7 or may be integral therewith. Each spring comprises inner and outer tubes 11&lt;SP&gt;1&lt;/SP&gt; with intermediate rubber members 11 secured by vulcanizing. The prestressing of the springs to suit the weight of the electrode is adjustable by a ring 4 screwed into the housing and having a pointer 16 co-operating with a scale on the housing.

mbn Huw? FIPSAS@ Sept. 11, 1962 G. KINTZEL ELECTROMAGNETICALLY ENERGIZED OSCILLATING HEAD FOR SPARK ERosIoN MACHINE Flled July 2o 1961 United States Patent O 3,053,965 ELECTRMAGNETICALLY ENERGIZED (BSCH.-

LATIN G HEAD FOR SPARK "EROSION MAC Gerhard Kintzel, Langen, Hessen, Germany, assigner to Nassovia Werlrzeugmnsciiinenfabrik G.n1.b.H., Hessen,

Germany, a company of Germany Filed July 20, 1961, Ser. No. 125,566 Claims priority, application Germany uly 23, 1966 7 Claims. (Cl. 219-69) The present invention relates to an oscillating head for a spark erosion machine for oscillating the electrode of the machine electromagnetically in its direction of feed, and more particularly it relates to a novel and very advantageous design and construction of the electrode supporting member and its manner of suspension for maintaining the amplitude of the oscillations of the electrode as constant as possible.

Such oscillating heads are employed in spark erosion machines for eroding very hard materials at particular points by means of sparks so as to form recesses, bores, grooves, or the like in the respective workpieces. The oscillatory movement of the electrode which is produced by the oscillating head in the direction of feed results even in narrow eroded bores in a pumping effect upon the liquid which covers the workpiece and the electrode so that this liquid will ilush away continuously the eroded metal particles and the burned residue of the liquid. This pumping and iiushing action considerably increases the accuracy of the eroding action and reduces the length of time required for the eroding process.

The oscillating heads of prior spark erosion machines are usually provided with an electrode supporting meniber which is preferably shaftlike and suspended on spring elements, for example, metal springs or diaphragms of rubber or metal, so as to be freely oscillating in the axial direction. This electrode supporting member is set into oscillation by means of an electromagnet which is energized by an alternating current or pulsating direct current through an intermediate air gap.

These prior oscillating heads have the disadvantage that any change in the weight of the electrode due to the consumption therof results in a change of the amplitude of its oscillation. Although the resulting deviation from the best possible oscillating conditions may be partly compensated electrically, the means required for this purpose are very expensive.

It is an object of the present invention to provide an oscillating head for spark erosion machines which is very inexpensive and completely yovercomes the abovementioned disadvantages by suspending the electrode supporting member on at least two spring elements which are under an initial ten-sion relative to each other in the axial direction of the electrode supporting member, and by providing simple means for adjusting the tension of these spring elements. It is thus possible to adjust the restoring force of the freely oscillating system in a very simple manner in accordance with the varying total weight of the oscillating parts and to maintain the natural frequency substantially in resonance with the frequency of excitation of the electromagnet.

According to a preferred feature of the invention it is of great advantage if the oscillating head is designed so that simultaneously with an adjustment of the spring tension the width of the air gap which is eiective in the direction of oscillation within the magnetic circuit producing the oscillations is also adjusted, but in a reverse sense, yso that the traction of the electromagnet will always be in accordance with the prevailing weight of the electrode. This may be attained according to the invention in a very simple manner by a preferably axial adjustment of the outer supporting points of those spring ICC elements which act in the same direction as the electromagnet upon the electrode supporting member. In this manner it is possible to omit entirely any electrical control of the energizing current which was required for the operation of the previous oscillating heads.

According to another feature of the invention it is advisable to design the spring elements in the form of tubular silent blocks which concentrically surround the electrode supporting member and are arranged in the axial direction behind and spaced from each other. Each of these silent blocks may consist, for example, of a pair of concentrical metal tubes lbetween which an annular resilient body, for example, of rubber, is interposed which is secured to these metal tubes, for example, by vulcanization. Such silent blocks have the considerable advantage over metal springs that fatigue breakdowns, which may occur with metal springs after they have been used only for a relatively short time, will be avoided, that the supervision and servicing of the apparatus will be considerably simplified, and that the useful life of the oscillating head will be greatly increased.

These as well as other objects, features, and advantagesVV of the present invention will become more clearly apparent from the following detailed description thereof, particularly when the same is read w-ith refer/,ence to the accompanying drawing which illustrates an oscillating head according to the invention diagramma-tically in cross section.

Referring to the drawing, the oscillating head according to the invention comprises a cylindrical housing 1 which is open toward the lower side. An electromagnet 2 which is, for example, pot-shaped, is secured, for example, by means of a screw 3, to the inside of the upper end wall of housing 1 land coaxially thereto. The open lower end of housing 1 is provided with inner screw threads into which a flanged setting ring 4 is screwed which is provided with a central cylindrical bore in which a shaftlike electrode supporting member 5 is mounted so as -to be slidable in its axial direction Within this bore. The part of the electrode supporting member 5 which is disposed within housing 1 has a reduced diameter so as to forma shoulder 6, and its inner end is provided with screw threads on which a cup-shaped armature 7 is screwed, the closed end of which is disposed directly in front of electromagnet 2 but so as to be separated therefrom by an air gap `8. Instead of making armature 7 as a separate part, it may also be integral with the electrode supporting member 5.

The lower reduced end of armature 7 is slidable within a guide ring 9 which engages radially against the cylindrical inner wall of housing 1 and axially in the direction toward electromagnet 2 against a shoulder 10 at the inside of the housing.

The reduced part of the electrode supporting member 5 carries two annular cylindrical silent blocks 11 and 12 each of which consists of a pair of outer and inner coaxial metal tubes 11' o-r 12 and intermediate annular resilient members of rubber or the like which are secured to the metal tubes, for example, by vulcanization. The inner tubes of the silent blocks 11 and 12 are spaced from each other by a spacing sleeve 13 and both inner tubes together with the spacing sleeve are clamped between shoulder 6 on the electrode supporting member 5 and the threaded end of armature 7. The outer diameter of spacing sleeve 13 is Substantially equal to the outer diameter of the inner metal tubes of the silent blocks 11 and 12 so that the resilient members of the silent blocks can bulge in both axial directions. The outer metal tubes 11 and 12 of the silent blocks engage radially with the cylindrical inner wall of housing 1 `and their opposite outer ends engage in the axial direction with spacing rings 14 and 15, respectively, which in turn engage at their other side with guide ring 9 and the inner end of setting ring 4, respectively. Since the two outer tubes 1.1 and 12 of the silent blocks 11 and 12 are spaced from each other and do not engage upon a spacing ring, setting ring 4 may be screwed into housing 1 as far as may be desired and until the two outer tubes of the silent blocks 11-and 12 abut against each other. FT he two silent blocks =11 and 12 may thus be given any desired initial tension relative to each other.

Since the outer metal tube 11 of the upper silent block 11 will not be moved when setting ring 4 is being adjusted, but this silent block when under tension will bulge toward the magnet, an increased bulging caused by an increased tension will by itself reduce the width of the air gap 8, whereby the traction of the magnet will be increased, while a reduced tension will result in an enlargement of air gap 8.

Setting ring 4 is preferably provided with markings, for example, with a pointer 16 which in Iassociation with markings on housing 1 which are calibrated in accordance with the weight of the electrode will then indicate the position of setting ring 4 which is required to produce the necessary tension of the silent blocks 11 and 12.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1s:

l. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting member adapted to receive an electrode slidably guided in the axial direction within said housing, at least two resilient elements mounted in said housing and acting upon said member and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, an electromagnet secured within said housing and spaced by an air gap from the inner end of said member for oscillating said member, and means for adjusting the initial tension of said resilient elements.

2. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting member adapted to receive an electrode slidably guided in the axial direction within said housing, at least two resilient elements mounted in said housing and acting upon said member and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, an electromagnet secured within said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member, and means for adjusting the initial tension of at least one of said resilient elements so that, when the tension of said element is increased, the eifective width of said air gap as seen in the direction of oscillation is reduced and when the tension of said element is reduced, the width of said air gap is increased.

3. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting member adapted to lreceive an electrode slidably guided in the axial direction within said housing, at least two annular resilient elements in said housing having inner surfaces rigidly connected to said member and outer surfaces engaging with the inner wall of said housing, said resilient elements being under 'an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, an electromagnet secured within said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member and adjusting means acting upon the outer surfaces of at least one of said resilient elements acting upon said member in the same direction as said electromagnet for adjusting said outer surfaces in the axial direction so as thereby to adjust the initial ten- Sion of said resilient element so that, when the tension of said element is increased, the effective width of said air gap as seen in the direction of oscillation is reduced and when the tension of said element is reduced, the Width of said air gap is increased.

4. An oscillating head for a spark erosion machine comprising a tubular housing, a sliaftlike electrode supporting member adapted to receive an electrode slidably guided in the axial direction within said housing, at least two silent blocks concentrically surrounding and connected to said member `and disposed axially behind and spaced from each other within said housing and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, an electromagnet secured within said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member, and means for adjusting the initial tension of at least one of said silent blocks so that, when the tension of said silent block is increased, the effective width of said air gap as seen in the direction of oscillation is reduced and when the tension of said silent block is increased, the width of said air gap is increased.

5. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting member adapted to receive an electrode slidably lguided in the axial direction within said housing, at least two silent blocks concentrically surrounding and connected to said member and disposed axially behind and spaced from each other within said housing and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, each of said silent blocks comprising a pair of metal tubes disposed concentrically within each other and an annular block of a rubberlike material intermediate and secured to said metal tubes, an electromagnet secured within said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member, and means for adjusting the initial tension of at least one of said silent blocks so that, when the tension of said silent block is increased, the effective width of said air gap as seen in the direction of oscillation is reduced and when the tension of said silent block is increased, the Width of said air gap is increased.

6. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting `member adapted to receive an electrode slidably guided in the axial direction within said housing, at least two silent blocks concentrically surrounding and connected to said member and disposed axially behind and spaced from each other within said housing and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, each of said silent blocks comprising a pair of metal tubes disposed concentrically within each other and an annular block of a rubberlike material intermediate and secured to said metal tubes, an electromagnet secured within said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member, and a setting ring screwed into the other end of said housing and acting in the axial direction upon the outer metal tube of at least one of said silent blocks for adjusting the initial tension of said -silent block so that when the tenison of said silent block is increased, the effective width of said air gap as seen in the direction of oscillation is reduced and when the Itension of said silent block is increased, the width lof said -air gap is increased.

7. An oscillating head for a spark erosion machine comprising a tubular housing, a shaftlike electrode supporting member adapted to receive an electrode slidably guided in the axial direction within said housing, at least two resilient elements mounted in said housing and acting upon said member and being under an initial tension in the axial direction relative to each other and permitting said member to oscillate freely in its axial direction, an electromagnet secured within -said housing near one end thereof and spaced by an air gap from the inner end of said member for oscillating said member, means for adjusting the initial tension of at least one of said silent blocks, and associated calibration markings on said adjusting means and on said housing permitting the differ- References Cited in the le of this patent UNITED STATES PATENTS McKechnie et al Mar. 28, 1950 McKechnie Oct. 6, 1953 McKechnie Iuly 3, 1956 McKechnie Sept. 8, 1959 

